Generally, a molten carbonate fuel cell is an electrochemical power generation device for producing electricity using a hydrogen oxidation reaction and an oxygen reduction reaction.H2+CO32−H2O+CO2+2e−(anode: oxidation reaction)  [Reaction Formula 1]½O2+Co2+2e−CO32−(cathode: reduction reaction)  [Reaction Formula 2]
As shown in FIG. 1, a molten carbonate fuel cell includes an anode 100, a matrix 200 and a cathode 300. The matrix 200 is impregnated with an electrolyte, thus causing ions to flow smoothly. The anode (fuel electrode) 100 serves to produce electrons by oxidizing fuel gas (generally, hydrogen) supplied through an anode current collector 110, and the cathode 300 serves to produce carbonate ions (CO32−) by reacting the ions produced by the anode with oxygen or air and carbon dioxide supplied through a cathode current collector 310 and thus to consume electric charges. In this case, the carbonate ions produced by the cathode 300 is transferred from the cathode 300 to the anode 100 through the matrix 200 located between the anode 100 and the cathode 300, and the ions produced by the anode 100 flow through an external circuit. Therefore, a molten carbonate fuel cell must have an electrolyte distribution suitable for each component, and can produce electricity only when three-phase boundaries (fuel gas/liquid electrolyte/solid electrode) are sufficiently formed at an anode and a cathode.
An anode of a molten carbonate fuel cell must have good electrical conductivity, a sufficient reactive area for an electrochemical reaction and wettability suitable for an electrolyte. For this reason, nickel (Ni), which has excellent electrochemical activity, has been used as an anode of a molten carbonate fuel cell, and, particularly, a porous nickel (Ni) anode has been used in order to increase a reactive area between fuel gas and an electrolyte. However, a molten carbonate fuel cell is problematic in that it operates at a high temperature of 650° C., and operating pressure is applied to its stack in order to seal gas and to decrease the contact resistance between its components, and thus sintering and creep of the porous structure of an electrode easily occur. Further, a molten carbonate fuel cell is problematic in that the redistribution of an electrolyte and the decrease in the reactive area of an electrode are caused by the change of pore distribution, so that a matrix is easily cracked and crossover between fuel and oxygen occur.
During long-term operation of a molten carbonate fuel cell (MCFC), the deformation of an electrode structure, occurring in an anode, is chiefly caused by sintering and creep. The reason for this is that, since an electrode material of an anode exists in the form of metal, when the molten carbonate fuel cell (MCFC) is operated for a long time under a high temperature of 650° C. and a operating pressure of several Kgf/cm2, sintering and creep phenomena occur. For this reason, in order to decrease the change in the material properties of an anode, such as anode sintering, pore growth, shrinkage, specific surface area loss and the like, which are causes of the deterioration in the performance of the molten carbonate fuel cell (MCFC) during the long-term operation of the molten carbonate fuel cell (MCFC), recently, research for optimizing the material properties of the anode by manufacturing an anode made of Ni—Al alloy, Ni—Cr alloy, Ni—Al—Cr alloy and the like selected from among Al, Ni, Cr and the like has been actively researched.
Referring to conventional methods of manufacturing an anode, Korean Patent Application No. 10-1999-0046260 discloses a method of manufacturing an alloy anode for a molten carbonate fuel cell, in which the high-temperature creep properties of an anode are improved using alumina formed by sequentially oxidizing and reducing an anode green sheet, and Korean Patent Application No. 10-2001-0067917 discloses a method of manufacturing an anode for a molten carbonate fuel cell coated with porous ceramic film, in which the high-temperature long-term stability of the molten carbonate fuel cell is ensured by coating the inner surfaces of pores with alumina or ceria. Further, Korean Unexamined Patent Application Publication No. 10-2003-0070725 discloses a method of manufacturing an anode for a molten carbonate fuel cell, in which the high-temperature compression resistance of an anode is improved by manufacturing the anode using nickel (Ni) and copper (Cu) and the sintering characteristics of Ni—Al alloy is improved by adding pure nickel (Ni) thereto.
However, the above methods are problematic in that a large-sized anode cannot be manufactured due to the control of microstructure, and in that production costs are increased because processes are complicated and a heat treatment process is performed.
In order to solve the above problems, Korean Unexamined Patent Application Publication No. 10-2003-0070725 discloses a case where an anode is directly inserted into a stack without heat treatment. However, the long term properties of the anode are not described in this patent document, and it is known through various research that the high-temperature creep properties of an anode cannot be improved using this method. Further, U.S. Pat. No. 5,558,947, filed by Energy Research Corp., discloses a rechargeable battery system in which the strength and long-term stability of an anode is increased and ensured by preparing a tape and then laminating the tape with a punching screen, but is disadvantageous in that it is difficult to fabricate a punching screen, and the punching screen is expensive, and thus it is difficult to ensure economical efficiency. Furthermore, U.S. Pat. No. 6,719,946, filed by FuelCell Energy Inc., discloses an anode support formed of a three-dimensional interconnected porous nickel plaque fabricated by sintering a bed of pure metallic nickel powder particles, but is also disadvantageous in that the anode support must be fabricated and then heat-treated, thus increasing production costs.
Therefore, the present inventors found a method of manufacturing an anode, in which an anode green sheet is fabricated, and then a reinforcing layer 120 is placed on the anode green sheet and then laminated, so that a large-size anode having excellent long-term properties can be produced in large quantities at low cost. Based on this finding, the present invention was completed.